Flat-Focal-Plane Dual-Metasurface Lens for Low Scan Loss and Sidelobe Level of a Metalens Antenna

A flat-focal-plane dual-metasurface lens (dual-metalens) is presented to lower the scan loss and sidelobe level (SLL) of a metalens antenna. The dual-metalens consists of two metasurfaces with different phase shift distributions and focal ratios. This proposed metalens ensures that the focal points of 0° and 30° incident plane waves are on a flat plane, which lowers the beam scan loss and SLLs by reducing the comatic aberration of the metalens. The measurement shows that the proposed antenna achieves a maximum gain of 26.6 dBi at 27.5 GHz with a 10 $\lambda _{0}$ -diameter aperture, where $\lambda _{0}$ is the wavelength at 28 GHz in free space. The antenna only has a 1.9 dB scan loss with an SLL lower than −14.1 dB at 28 GHz for a scan angle of ±29°. The 3 dB gain frequency range is from 26.8 to 29.3 GHz, which is suitable for the 5G millimeter wave wireless communication.